Implantable neurostimulation systems have proven therapeutic in a wide variety of diseases and disorders. Pacemakers and Implantable Cardiac Defibrillators (ICDs) have proven highly effective in the treatment of a number of cardiac conditions (e.g., arrhythmias). Spinal Cord Stimulation (SCS) systems have long been accepted as a therapeutic modality for the treatment of chronic pain syndromes, and the application of tissue stimulation has begun to expand to additional applications, such as angina pectoris and incontinence. Further, in recent investigations, Peripheral Nerve Stimulation (PNS) systems have demonstrated efficacy in the treatment of chronic pain syndromes and incontinence, and a number of additional applications are currently under investigation. More pertinent to the present inventions described herein, Deep Brain Stimulation (DBS) has been applied therapeutically for well over a decade for the treatment of neurological disorders, including Parkinson's Disease, essential tremor, dystonia, and epilepsy, to name but a few. Further details discussing the treatment of diseases using DBS are disclosed in U.S. Pat. Nos. 6,845,267, 6,845,267, and 6,950,707, which are expressly incorporated herein by reference.
Each of these implantable neurostimulation systems typically includes one or more electrode carrying stimulation leads, which are implanted at the desired stimulation site, and a neurostimulator implanted remotely from the stimulation site, but coupled either directly to the stimulation lead(s) or indirectly to the stimulation lead(s) via a lead extension. The neurostimulation system may further comprise a handheld external control device to remotely instruct the neurostimulator to generate electrical stimulation pulses in accordance with selected stimulation parameters. Typically, the stimulation parameters programmed into the neurostimulator can be adjusted by manipulating controls on the external control device to modify the electrical stimulation provided by the neurostimulator system to the patient.
Thus, in accordance with the stimulation parameters programmed by the external control device, electrical pulses can be delivered from the neurostimulator to the stimulation electrode(s) to stimulate or activate a volume of tissue in accordance with a set of stimulation parameters and provide the desired efficacious therapy to the patient. The best stimulus parameter set will typically be one that delivers stimulation energy to the volume of tissue that must be stimulated in order to provide the therapeutic benefit (e.g., treatment of movement disorders), while minimizing the volume of non-target tissue that is stimulated. A typical stimulation parameter set may include the electrodes that are acting as anodes or cathodes, as well as the amplitude, duration, and rate of the stimulation pulses.
Significantly, non-optimal electrode placement and stimulation parameter selections may result in excessive energy consumption due to stimulation that is set at too high an amplitude, too wide a pulse duration, or too fast a frequency; inadequate or marginalized treatment due to stimulation that is set at too low an amplitude, too narrow a pulse duration, or too slow a frequency; or stimulation of neighboring cell populations that may result in undesirable side effects.
The large number of electrodes available, combined with the ability to generate a variety of complex stimulation pulses, presents a huge selection of stimulation parameter sets to the clinician or patient. To facilitate such selection, the clinician generally programs the external control device, and if applicable the neurostimulator, through a computerized programming system. This programming system can be a self-contained hardware/software system, or can be defined predominantly by software running on a standard personal computer (PC). The PC or custom hardware may actively control the characteristics of the electrical stimulation generated by the neurostimulator to allow the optimum stimulation parameters to be determined based on patient feedback and to subsequently program the external control device with the optimum stimulation parameters.
When electrical leads are implanted within the patient, the computerized programming system may be used to instruct the neurostimulator to apply electrical stimulation to test placement of the leads and/or electrodes, thereby assuring that the leads and/or electrodes are implanted in effective locations within the patient. Once the leads are correctly positioned, a fitting procedure, which may be referred to as a navigation session, may be performed using the computerized programming system to program the external control device, and if applicable the neurostimulator, with a set of stimulation parameters that best addresses the neurological disorder(s).
As physicians and clinicians become more comfortable with implanting neurostimulation systems and time in the operating room decreases, post-implant programming sessions are becoming a larger portion of process. Furthermore, because the body tends to adapt to the specific stimulation parameters currently programmed into a neurostimulation system, follow-up programming procedures are often needed. For example, the brain is dynamic (e.g., due to disease progression, motor re-learning, or other changes), and a program (i.e., a set of stimulation parameters) that is useful for a period of time may not maintain its effectiveness and/or the expectations of the patient may increase. Thus, after the DBS system has been implanted and fitted, the patient may have to schedule another visit to the physician in order to adjust the stimulation parameters of the DBS system if the treatment provided by the implanted DBS system is no longer effective or otherwise is not therapeutically or operationally optimum due to, e.g., disease progression, motor re-learning, or other changes.
Thus, post-implant programming of neurostimulation systems has become a very important part of providing effective therapy to a patient. There are a few issues with current programming methods that need to be addressed.
For example, despite the fact that computerized programming systems have been used to speed up the programming process, performing post-implant programming for an electrical stimulation system still be a relatively time-consuming process. As with many neurostimulation systems, stimulation provided by a DBS system can cause side effects. Current methods to minimize the side effects of neurostimulation include manually changing the stimulation parameters until the side effects are minimized. However, finding the balance between minimal side effects and optimal treatment is difficult to do manually—as there are many factors to evaluate. Furthermore, the physician or clinician that programs the neurostimulators are often trained by experience alone, and lack formal training in the theory of neurostimulation. Therefore, finding the optimal set of stimulation parameter can be hit and miss.
Regardless of the skill of the physician or clinician, these programming sessions can be especially lengthy when programming complicated neurostimulation systems, such as DBS systems, in contrast to other neurostimulation systems, such as SCS systems.
In particular, in some electrical stimulation treatments, the fitting procedure may be effectively directed in response to patient feedback. For example, in SCS for providing pain relief, patients can feel the effects of the stimulation pulses and the change in their pain status, and thus, may provide verbal feedback as to the efficacy of the stimulation, and thus, the proper location of the stimulation leads and/or electrodes and the stimulation parameters to be used in delivering the electrical pulses to the patient on a long-term basis. Unlike with SCS, patients receiving DBS usually cannot feel the effects of stimulation, and the effects of the stimulation may be difficult to observe, are typically subjective, or otherwise may take a long time to become apparent. This makes it difficult to set the stimulation parameters appropriately or otherwise select stimulation parameters that result in optimal treatment for the patient and/or optimal use of the stimulation resources.
Thus, obtaining an optimal program is difficult and sometimes not achieved, resulting in a fitting process that is extremely time consuming and tedious. Exacerbating this problem is the fact that the physician or clinician must manually change the stimulation parameters and evaluate the effects on the patient's symptoms, and therefore, must sit with the patient for the long duration of the programming process, which is a large time commitment.
Besides the problem of requiring a time-consuming programming session that must be manually administered by a physician or clinician, latency issues in the treatment of symptoms often prevent the optimal set of stimulation to be determined. For example, various symptoms of movement disorders, such as Parkinson's disease, take different lengths of time to be suppressed by electrical stimulation. Some symptoms take seconds (e.g., tremor), minutes (e.g., rigidity), or even hours (e.g., bradykinesia) to fade away. However, physicians and clinicians usually program patients at a pace that does not allow symptoms to fully disperse. As a result, they may miss or overlook the best stimulation parameters for treating the symptoms of Parkinson's disease.
While DBS systems have been disclosed that utilize a closed-loop method that involves sensing electrical signals within the brain of the patient and automatically adjusting the electrical stimulation delivered to a target region within the brain of the patient (see, e.g., U.S. Pat. No. 5,683,422), such a system requires the implantation of an additional lead within the brain or inclusion of complex implantable hardware providing updates to the stimulation parameter set. In addition, the electrical signals sensed within the brain are not easily correlatable to the disorder currently experienced by the patient. Furthermore, such a system is not designed to be used in a fitting procedure, including physical adjustment of the leads and programming of the stimulation parameters.
There, thus, remains a need for a DBS system that can be more easily fitted to a patient in order to optimize treatment of a patient suffering from a disease.